Three-dimensional memory device having an epitaxial vertical semiconductor channel and method for making the same

ABSTRACT

A semiconductor structure includes a memory die bonded to a support die. The memory die includes an alternating stack of insulating layers and electrically conductive layers located over a substrate including a single crystalline substrate semiconductor material, and memory stack structures extending through the alternating stack and containing a respective memory film and a respective vertical semiconductor channel including a single crystalline channel semiconductor material. The support die contains a peripheral circuitry.

FIELD

The present disclosure relates generally to the field of semiconductordevices, and particular to a three-dimensional memory device usingepitaxial vertical semiconductor channels and methods of manufacturingthe same.

BACKGROUND

Three-dimensional vertical NAND strings having one bit per cell aredisclosed in an article by T. Endoh et al., titled “Novel Ultra HighDensity Memory With A Stacked-Surrounding Gate Transistor (S-SGT)Structured Cell”, IEDM Proc. (2001) 33-36.

SUMMARY

According to an embodiment of the present disclosure, a semiconductorstructure includes a memory die bonded to a support die. The memory dieincludes an alternating stack of insulating layers and electricallyconductive layers located over a substrate including a singlecrystalline substrate semiconductor material, and memory stackstructures extending through the alternating stack and containing arespective memory film and a respective vertical semiconductor channelincluding a single crystalline channel semiconductor material. Thesupport die contains a peripheral circuitry.

According to another embodiment of the present disclosure a method offorming a semiconductor structure includes forming an alternating stackof insulating layers and spacer material layers over a substrate of amemory die, wherein the substrate includes a single crystallinesubstrate semiconductor material, and wherein the sacrificial materiallayers are formed as, or are subsequently replaced with, electricallyconductive layers, forming memory openings through the alternatingstack, forming memory films in the memory openings, filling volumes ofthe memory openings that are not filled with the memory films withsingle crystalline semiconductor channel material portions having adoping of a first conductivity type and in epitaxial alignment with thesingle crystalline substrate semiconductor material, and bonding asupport die containing peripheral circuitry to the memory die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic vertical cross-sectional view of an exemplarystructure after formation of a semiconductor material layer on asubstrate semiconductor layer according to an embodiment of the presentdisclosure.

FIG. 2 is a schematic vertical cross-sectional view of the exemplarystructure after formation of an alternating stack of insulating layersand sacrificial material layers according to an embodiment of thepresent disclosure.

FIG. 3 is a schematic vertical cross-sectional view of the exemplarystructure after formation of stepped terraces and a retro-steppeddielectric material portion according to an embodiment of the presentdisclosure.

FIG. 4A is a schematic vertical cross-sectional view of the exemplarystructure after formation of memory openings and support openingsaccording to an embodiment of the present disclosure.

FIG. 4B is a top-down view of the exemplary structure of FIG. 4A. Thevertical plane A-A′ is the plane of the cross-section for FIG. 4A.

FIGS. 5A-5G are sequential schematic vertical cross-sectional views of amemory opening within the exemplary structure during formation of amemory stack structure, and a drain region therein according to anembodiment of the present disclosure.

FIG. 6 is a schematic vertical cross-sectional view of the exemplarystructure after formation of memory stack structures and support pillarstructures according to an embodiment of the present disclosure.

FIG. 7A is a schematic vertical cross-sectional view of the exemplarystructure after formation of backside trenches according to anembodiment of the present disclosure.

FIG. 7B is a partial see-through top-down view of the exemplarystructure of FIG. 7A. The vertical plane A-A′ is the plane of theschematic vertical cross-sectional view of FIG. 7A.

FIG. 8 is a schematic vertical cross-sectional view of the exemplarystructure after formation of backside recesses according to anembodiment of the present disclosure.

FIGS. 9A-9D are sequential vertical cross-sectional views of a region ofthe exemplary structure during formation of electrically conductivelayers according to an embodiment of the present disclosure.

FIG. 10 is a schematic vertical cross-sectional view of the exemplarystructure at the processing step of FIG. 9D.

FIG. 11A is a schematic vertical cross-sectional view of the exemplarystructure after removal of a deposited conductive material from withinthe backside trench according to an embodiment of the presentdisclosure.

FIG. 11B is a partial see-through top-down view of the exemplarystructure of FIG. 11A. The vertical plane A-A′ is the plane of theschematic vertical cross-sectional view of FIG. 11A.

FIG. 12A is a schematic vertical cross-sectional view of the exemplarystructure after formation of an insulating spacer and a backside contactstructure according to an embodiment of the present disclosure.

FIG. 12B is a magnified view of a region of the exemplary structure ofFIG. 12A.

FIG. 13A is a schematic vertical cross-sectional view of the exemplarystructure after formation of additional contact via structures accordingto an embodiment of the present disclosure.

FIG. 13B is a top-down view of the exemplary structure of FIG. 13A. Thevertical plane A-A′ is the plane of the schematic verticalcross-sectional view of FIG. 13A.

FIG. 14 is a vertical cross-sectional view of the exemplary structureafter formation of a memory die including memory-side bonding pads.

FIG. 15 is a vertical cross-sectional view of the exemplary structureafter bonding a support die to the memory die according to an embodimentof the present disclosure.

FIG. 16 is a vertical cross-sectional view of the exemplary structureafter thinning the support die and forming external bonding padsaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

As the total number of word lines increases in the three-dimensionalmemory devices, vertical semiconductor channels of the vertical NANDstrings become longer, thereby decreasing the on-current for thevertical semiconductor channels. In order to vertically scale thethree-dimensional memory device and to provide stacking a greater numberof word lines, the on-current of the vertical semiconductor channels maybe increased in various disclosed embodiments by using epitaxialvertical semiconductor channels. Various embodiments disclosed hereinare directed to a three-dimensional memory device using epitaxialvertical semiconductor channels and methods of manufacturing the same,the various aspects of which are described below. The embodiments of thedisclosure may be used to form various structures including a multilevelmemory structure, non-limiting examples of which include semiconductordevices such as three-dimensional monolithic memory array devicescomprising a plurality of NAND memory strings.

The drawings are not drawn to scale. Multiple instances of an elementmay be duplicated where a single instance of the element is illustrated,unless absence of duplication of elements is expressly described orclearly indicated otherwise. Ordinals such as “first,” “second,” and“third” are used merely to identify similar elements, and differentordinals may be used across the specification and the claims of theinstant disclosure. The same reference numerals refer to the sameelement or similar element. Unless otherwise indicated, elements havingthe same reference numerals are presumed to have the same compositionand the same function. Unless otherwise indicated, a “contact” betweenelements refers to a direct contact between elements that provides anedge or a surface shared by the elements. As used herein, a firstelement located “on” a second element may be located on the exteriorside of a surface of the second element or on the interior side of thesecond element. As used herein, a first element is located “directly on”a second element if there exist a physical contact between a surface ofthe first element and a surface of the second element. As used herein, a“prototype” structure or an “in-process” structure refers to a transientstructure that is subsequently modified in the shape or composition ofat least one component therein.

As used herein, a “layer” refers to a material portion including aregion having a thickness. A layer may extend over the entirety of anunderlying or overlying structure, or may have an extent less than theextent of an underlying or overlying structure. Further, a layer may bea region of a homogeneous or inhomogeneous continuous structure that hasa thickness less than the thickness of the continuous structure. Forexample, a layer may be located between any pair of horizontal planesbetween, or at, a top surface and a bottom surface of the continuousstructure. A layer may extend horizontally, vertically, and/or along atapered surface. A substrate may be a layer, may include one or morelayers therein, or may have one or more layer thereupon, thereabove,and/or therebelow.

As used herein, a first surface and a second surface are “verticallycoincident” with each other if the second surface overlies or underliesthe first surface and there exists a vertical plane or a substantiallyvertical plane that includes the first surface and the second surface. Asubstantially vertical plane is a plane that extends straight along adirection that deviates from a vertical direction by an angle less than5 degrees. A vertical plane or a substantially vertical plane isstraight along a vertical direction or a substantially verticaldirection, and may, or may not, include a curvature along a directionthat is perpendicular to the vertical direction or the substantiallyvertical direction.

A monolithic three-dimensional memory array is a memory array in whichmultiple memory levels are formed above a single substrate, such as asemiconductor wafer, with no intervening substrates. The term“monolithic” means that layers of each level of the array are directlydeposited on the layers of each underlying level of the array. Incontrast, two dimensional arrays may be formed separately and thenpackaged together to form a non-monolithic memory device. For example,non-monolithic stacked memories have been constructed by forming memorylevels on separate substrates and vertically stacking the memory levels,as described in U.S. Pat. No. 5,915,167 titled “Three-dimensionalStructure Memory.” The substrates may be thinned or removed from thememory levels before bonding, but as the memory levels are initiallyformed over separate substrates, such memories are not true monolithicthree-dimensional memory arrays. The various three-dimensional memorydevices of the present disclosure include a monolithic three-dimensionalNAND string memory device, and may be fabricated using the variousembodiments described herein.

Generally, a semiconductor package (or a “package”) refers to a unitsemiconductor device that may be attached to a circuit board through aset of pins or solder balls. A semiconductor package may include asemiconductor chip (or a “chip”) or a plurality of semiconductor chipsthat are bonded throughout, for example, by flip-chip bonding or anotherchip-to-chip bonding. A package or a chip may include a singlesemiconductor die (or a “die”) or a plurality of semiconductor dies. Adie is the smallest unit that may independently execute externalcommands or report status. Typically, a package or a chip with multipledies is capable of simultaneously executing as many external commands asthe total number of planes therein. Each die includes one or moreplanes. Identical concurrent operations may be executed in each planewithin a same die, although there may be some restrictions. In case adie is a memory die, i.e., a die including memory elements, concurrentread operations, concurrent write operations, or concurrent eraseoperations may be performed in each plane within a same memory die. In amemory die, each plane contains a number of memory blocks (or “blocks”),which are the smallest unit that may be erased by in a single eraseoperation. Each memory block contains a number of pages, which are thesmallest units that may be selected for programming. A page is also thesmallest unit that may be selected to a read operation.

Referring to FIG. 1, an exemplary structure according to an embodimentof the present disclosure is illustrated, which may be used, forexample, to fabricate a device structure containing vertical NAND memorydevices. The exemplary structure includes a substrate (9, 10), whichincludes a single crystalline substrate semiconductor material, i.e., asingle crystalline semiconductor material located in a substrate. Thesubstrate (9, 10) may include a substrate semiconductor layer 9 and anoptional semiconductor material layer 10. The substrate semiconductorlayer 9 may be a semiconductor wafer or a semiconductor material layer,and may include at least one elemental semiconductor material (e.g.,single crystal silicon wafer or layer), at least one III-V compoundsemiconductor material, at least one II-VI compound semiconductormaterial, at least one organic semiconductor material, or othersemiconductor materials known in the art. The substrate (9, 10) may havea major surface 7, which may be, for example, a topmost surface of thesubstrate semiconductor layer 9. The major surface 7 may be asemiconductor surface. In one embodiment, the major surface 7 may be asingle crystalline semiconductor surface, such as a single crystallinesemiconductor surface. The entirety of the substrate (9, 10) may consistessentially of the single crystalline substrate semiconductor material,which may be single crystalline silicon. In one embodiment, the singlecrystalline substrate semiconductor material of the semiconductormaterial layer 10 may have a doping of a first conductivity type, whichmay be p-type or n-type. In one embodiment, various doped wells may beprovided in the upper portion of the substrate semiconductor layer 9 toelectrically isolate the semiconductor material layer 10 from thesubstrate semiconductor layer 9. For example, a plurality of p-njunctions may be used to provide a nested doped well structure.

As used herein, a “semiconducting material” refers to a material havingelectrical conductivity in the range from 1.0×10⁻⁵ S/m to 1.0×10⁵ S/m.As used herein, a “semiconductor material” refers to a material havingelectrical conductivity in the range from 1.0×10⁻⁵ S/m to 1.0 S/m in theabsence of electrical dopants therein, and is capable of producing adoped material having electrical conductivity in a range from 1.0 S/m to1.0×10⁵ S/m upon suitable doping with an electrical dopant. As usedherein, an “electrical dopant” refers to a p-type dopant that adds ahole to a valence band within a band structure, or an n-type dopant thatadds an electron to a conduction band within a band structure. As usedherein, a “conductive material” refers to a material having electricalconductivity greater than 1.0×10⁵ S/m. As used herein, an “insulatormaterial” or a “dielectric material” refers to a material havingelectrical conductivity less than 1.0×10⁻⁵ S/m. As used herein, a“heavily doped semiconductor material” refers to a semiconductormaterial that is doped with electrical dopant at a sufficiently highatomic concentration to become a conductive material either as formed asa crystalline material or if converted into a crystalline materialthrough an anneal process (for example, from an initial amorphousstate), i.e., to have electrical conductivity greater than 1.0×10⁵ S/m.A “doped semiconductor material” may be a heavily doped semiconductormaterial, or may be a semiconductor material that includes electricaldopants (i.e., p-type dopants and/or n-type dopants) at a concentrationthat provides electrical conductivity in the range from 1.0×10⁻⁵ S/m to1.0×10⁵ S/m. An “intrinsic semiconductor material” refers to asemiconductor material that is not doped with electrical dopants. Thus,a semiconductor material may be semiconducting or conductive, and may bean intrinsic semiconductor material or a doped semiconductor material. Adoped semiconductor material may be semiconducting or conductivedepending on the atomic concentration of electrical dopants therein. Asused herein, a “metallic material” refers to a conductive materialincluding at least one metallic element therein. All measurements forelectrical conductivities are made at the standard condition.

The optional semiconductor material layer 10, if present, may be formedon the top surface of the substrate semiconductor layer 9 by depositionof a single crystalline semiconductor material, for example, by anepitaxial deposition process. The deposited semiconductor material maybe the same as, or may be different from, the semiconductor material ofthe substrate semiconductor layer 9. The deposited semiconductormaterial may be any material that may be used for the substratesemiconductor layer 9 as described above. The single crystallinesemiconductor material of the semiconductor material layer 10 may be inepitaxial alignment with the single crystalline structure of thesubstrate semiconductor layer 9. The region in which a memory array issubsequently formed is herein referred to as a memory array region 100.A staircase region 300 for subsequently forming stepped terraces ofelectrically conductive layers may be provided adjacent to the memoryarray region 100.

Referring to FIG. 2, a stack of an alternating plurality of firstmaterial layers (which may be insulating layers 32) and second materiallayers (which may be sacrificial material layer 42) is formed over thetop surface of the substrate (9, 10). As used herein, a “material layer”refers to a layer including a material throughout the entirety thereof.As used herein, an alternating plurality of first elements and secondelements refers to a structure in which instances of the first elementsand instances of the second elements alternate. Each instance of thefirst elements that is not an end element of the alternating pluralityis adjoined by two instances of the second elements on both sides, andeach instance of the second elements that is not an end element of thealternating plurality is adjoined by two instances of the first elementson both ends. The first elements may have the same thickness throughout,or may have different thicknesses. The second elements may have the samethickness throughout, or may have different thicknesses. The alternatingplurality of first material layers and second material layers may beginwith an instance of the first material layers or with an instance of thesecond material layers, and may end with an instance of the firstmaterial layers or with an instance of the second material layers. Inone embodiment, an instance of the first elements and an instance of thesecond elements may form a unit that is repeated with periodicity withinthe alternating plurality.

Each first material layer includes a first material, and each secondmaterial layer includes a second material that is different from thefirst material. In one embodiment, each first material layer may be aninsulating layer 32, and each second material layer may be a sacrificialmaterial layer. In this case, the stack may include an alternatingplurality of insulating layers 32 and sacrificial material layers 42,and constitutes a prototype stack of alternating layers comprisinginsulating layers 32 and sacrificial material layers 42.

The stack of the alternating plurality is herein referred to as analternating stack (32, 42). In one embodiment, the alternating stack(32, 42) may include insulating layers 32 composed of the firstmaterial, and sacrificial material layers 42 composed of a secondmaterial different from that of insulating layers 32. The first materialof the insulating layers 32 may be at least one insulating material. Assuch, each insulating layer 32 may be an insulating material layer.Insulating materials that may be used for the insulating layers 32include, but are not limited to, silicon oxide (including doped orundoped silicate glass), silicon nitride, silicon oxynitride,organosilicate glass (OSG), spin-on dielectric materials, dielectricmetal oxides that are commonly known as high dielectric constant(high-k) dielectric oxides (e.g., aluminum oxide, hafnium oxide, etc.)and silicates thereof, dielectric metal oxynitrides and silicatesthereof, and organic insulating materials. In one embodiment, the firstmaterial of the insulating layers 32 may be silicon oxide.

The second material of the sacrificial material layers 42 is asacrificial material that may be removed selective to the first materialof the insulating layers 32. As used herein, a removal of a firstmaterial is “selective to” a second material if the removal processremoves the first material at a rate that is at least twice the rate ofremoval of the second material. The ratio of the rate of removal of thefirst material to the rate of removal of the second material is hereinreferred to as a “selectivity” of the removal process for the firstmaterial with respect to the second material.

The sacrificial material layers 42 may comprise an insulating material,a semiconductor material, or a conductive material. The second materialof the sacrificial material layers 42 may be subsequently replaced withelectrically conductive electrodes which may function, for example, ascontrol gate electrodes of a vertical NAND device. Non-limiting examplesof the second material include silicon nitride, an amorphoussemiconductor material (such as amorphous silicon), and apolycrystalline semiconductor material (such as polysilicon). In oneembodiment, the sacrificial material layers 42 may be spacer materiallayers that comprise silicon nitride or a semiconductor materialincluding at least one of silicon and germanium.

In one embodiment, the insulating layers 32 may include silicon oxide,and sacrificial material layers may include silicon nitride sacrificialmaterial layers. The first material of the insulating layers 32 may bedeposited, for example, by chemical vapor deposition (CVD). For example,if silicon oxide is used for the insulating layers 32, tetraethylorthosilicate (TEOS) may be used as the precursor material for the CVDprocess. The second material of the sacrificial material layers 42 maybe formed, for example, CVD or atomic layer deposition (ALD).

The sacrificial material layers 42 may be suitably patterned so thatconductive material portions to be subsequently formed by replacement ofthe sacrificial material layers 42 may function as electricallyconductive electrodes, such as the control gate electrodes of themonolithic three-dimensional NAND string memory devices to besubsequently formed. The sacrificial material layers 42 may comprise aportion having a strip shape extending substantially parallel to themajor surface 7 of the substrate.

The thicknesses of the insulating layers 32 and the sacrificial materiallayers 42 may be in a range from 20 nm to 50 nm, although lesser andgreater thicknesses may be used for each insulating layer 32 and foreach sacrificial material layer 42. The number of repetitions of thepairs of an insulating layer 32 and a sacrificial material layer (e.g.,a control gate electrode or a sacrificial material layer) 42 may be in arange from 2 to 1,024, and typically from 8 to 256, although a greaternumber of repetitions may also be used. The top and bottom gateelectrodes in the stack may function as the select gate electrodes. Inone embodiment, each sacrificial material layer 42 in the alternatingstack (32, 42) may have a uniform thickness that is substantiallyinvariant within each respective sacrificial material layer 42.

While the present disclosure is described using an embodiment in whichthe spacer material layers are sacrificial material layers 42 that aresubsequently replaced with electrically conductive layers, embodimentsare expressly contemplated herein in which the sacrificial materiallayers are formed as electrically conductive layers. In suchembodiments, steps for replacing the spacer material layers withelectrically conductive layers may be omitted.

Optionally, an insulating cap layer 70 may be formed over thealternating stack (32, 42). The insulating cap layer 70 includes adielectric material that is different from the material of thesacrificial material layers 42. In one embodiment, the insulating caplayer 70 may include a dielectric material that may be used for theinsulating layers 32 as described above. The insulating cap layer 70 mayhave a greater thickness than each of the insulating layers 32. Theinsulating cap layer 70 may be deposited, for example, by chemical vapordeposition. In one embodiment, the insulating cap layer 70 may be asilicon oxide layer.

Referring to FIG. 3, stepped surfaces are formed by patterning a portionof the alternating stack (32, 42) in the staircase region 300. Theregion of the stepped surfaces may also be referred to as a terraceregion. As used herein, “stepped surfaces” refer to a set of surfacesthat include at least two horizontal surfaces and at least two verticalsurfaces such that each horizontal surface is adjoined to a firstvertical surface that extends upward from a first edge of the horizontalsurface, and is adjoined to a second vertical surface that extendsdownward from a second edge of the horizontal surface. A stepped cavityis formed within the volume from which portions of the alternating stack(32, 42) are removed through formation of the stepped surfaces. A“stepped cavity” refers to a cavity having stepped surfaces.

The terrace region is formed in the staircase region 300, which isformed adjacent to the memory array region 100. The stepped cavity mayhave various stepped surfaces such that the horizontal cross-sectionalshape of the stepped cavity changes in steps as a function of thevertical distance from the top surface of the substrate (9, 10). In oneembodiment, the stepped cavity may be formed by repetitively performinga set of processing steps. The set of processing steps may include, forexample, an etch process of a first type that vertically increases thedepth of a cavity by one or more levels, and an etch process of a secondtype that laterally expands the area to be vertically etched in asubsequent etch process of the first type. As used herein, a “level” ofa structure including alternating plurality is defined as the relativeposition of a pair of a first material layer and a second material layerwithin the structure.

Each sacrificial material layer 42 other than a topmost sacrificialmaterial layer 42 within the alternating stack (32, 42) laterallyextends farther than any overlying sacrificial material layer 42 withinthe alternating stack (32, 42) in the terrace region. The terrace regionincludes stepped surfaces of the alternating stack (32, 42) thatcontinuously extend from a bottommost layer within the alternating stack(32, 42) to a topmost layer within the alternating stack (32, 42).

Each vertical step of the stepped surfaces may have a height of one ormore pairs of an insulating layer 32 and a sacrificial material layer42. In one embodiment, each vertical step may have the height of asingle pair of an insulating layer 32 and a sacrificial material layer42. In another embodiment, multiple “columns” of staircases may beformed along a first horizontal direction hd1 such that each verticalstep has the height of a plurality of pairs of an insulating layer 32and a sacrificial material layer 42, and the number of columns may be atleast the number of the plurality of pairs. Each column of staircase maybe vertically offset from one another such that each of the sacrificialmaterial layers 42 has a physically exposed top surface in a respectivecolumn of staircases. In the illustrative example, two columns ofstaircases are formed for each block of memory stack structures to besubsequently formed such that one column of staircases providephysically exposed top surfaces for odd-numbered sacrificial materiallayers 42 (as counted from the bottom) and another column of staircasesprovide physically exposed top surfaces for even-numbered sacrificialmaterial layers (as counted from the bottom). Configurations usingthree, four, or more columns of staircases with a respective set ofvertical offsets from the physically exposed surfaces of the sacrificialmaterial layers 42 may also be used. Each sacrificial material layer 42has a greater lateral extent, at least along one direction, than anyoverlying sacrificial material layers 42 such that each physicallyexposed surface of any sacrificial material layer 42 does not have anoverhang. In one embodiment, the vertical steps within each column ofstaircases may be arranged along the first horizontal direction hd1, andthe columns of staircases may be arranged along a second horizontaldirection hd2 that is perpendicular to the first horizontal directionhd1. In one embodiment, the first horizontal direction hd1 may beperpendicular to the boundary between the memory array region 100 andthe staircase region 300.

A retro-stepped dielectric material portion 65 (i.e., an insulating fillmaterial portion) may be formed in the stepped cavity by deposition of adielectric material therein. For example, a dielectric material such assilicon oxide may be deposited in the stepped cavity. Excess portions ofthe deposited dielectric material may be removed from above the topsurface of the insulating cap layer 70, for example, by chemicalmechanical planarization (CMP). The remaining portion of the depositeddielectric material filling the stepped cavity constitutes theretro-stepped dielectric material portion 65. As used herein, a“retro-stepped” element refers to an element that has stepped surfacesand a horizontal cross-sectional area that increases monotonically as afunction of a vertical distance from a top surface of a substrate onwhich the element is present. In embodiments in which silicon oxide isused for the retro-stepped dielectric material portion 65, the siliconoxide of the retro-stepped dielectric material portion 65 may, or maynot, be doped with dopants such as B, P, and/or F.

Optionally, drain select level isolation structures 72 may be formedthrough the insulating cap layer 70 and a subset of the sacrificialmaterial layers 42 located at drain select levels. The drain selectlevel isolation structures 72 may be formed, for example, by formingdrain select level isolation trenches and filling the drain select levelisolation trenches with a dielectric material such as silicon oxide.Excess portions of the dielectric material may be removed from above thetop surface of the insulating cap layer 70.

Referring to FIGS. 4A and 4B, a lithographic material stack (not shown)including at least a photoresist layer may be formed over the insulatingcap layer 70 and the retro-stepped dielectric material portion 65, andmay be lithographically patterned to form openings therein. The openingsinclude a first set of openings formed over the memory array region 100and a second set of openings formed over the staircase region 300. Thepattern in the lithographic material stack may be transferred throughthe insulating cap layer 70 or the retro-stepped dielectric materialportion 65, and through the alternating stack (32, 42) by at least oneanisotropic etch that uses the patterned lithographic material stack asan etch mask. Portions of the alternating stack (32, 42) underlying theopenings in the patterned lithographic material stack are etched to formmemory openings 49 in the memory array region 100 and support openings19 in the staircase region 300. As used herein, a “memory opening”refers to a structure in which memory elements, such as a memory stackstructure, is subsequently formed. As used herein, a “support opening”refers to a structure in which a support structure (such as a supportpillar structure) that mechanically supports other elements issubsequently formed. The memory openings 49 are formed through theinsulating cap layer 70 and the entirety of the alternating stack (32,42) in the memory array region 100. The support openings 19 are formedthrough the retro-stepped dielectric material portion 65 and the portionof the alternating stack (32, 42) that underlie the stepped surfaces inthe staircase region 300.

The memory openings 49 extend through the entirety of the alternatingstack (32, 42). The support openings 19 extend through a subset oflayers within the alternating stack (32, 42). The chemistry of theanisotropic etch process used to etch through the materials of thealternating stack (32, 42) may alternate to optimize etching of thefirst and second materials in the alternating stack (32, 42). Theanisotropic etch may be, for example, a series of reactive ion etches.The sidewalls of the memory openings 49 and the support openings 19 maybe substantially vertical, or may be tapered. The patterned lithographicmaterial stack may be subsequently removed, for example, by ashing.

The memory openings 49 and the support openings 19 may extend from thetop surface of the alternating stack (32, 42) to at least the horizontalplane including the topmost surface of the semiconductor material layer10. In one embodiment, an overetch into the semiconductor material layer10 may be optionally performed after the top surface of thesemiconductor material layer 10 is physically exposed at a bottom ofeach memory opening 49 and each support opening 19. The overetch may beperformed prior to, or after, removal of the lithographic materialstack. In other words, the recessed surfaces of the semiconductormaterial layer 10 may be vertically offset from the un-recessed topsurfaces of the semiconductor material layer 10 by a recess depth. Therecess depth may be, for example, in a range from 1 nm to 50 nm,although lesser and greater recess depths may also be used. The overetchis optional, and may be omitted. If the overetch is not performed, thebottom surfaces of the memory openings 49 and the support openings 19may be coplanar with the topmost surface of the semiconductor materiallayer 10.

Each of the memory openings 49 and the support openings 19 may include asidewall (or a plurality of sidewalls) that extends substantiallyperpendicular to the topmost surface of the substrate. A two-dimensionalarray of memory openings 49 may be formed in the memory array region100. A two-dimensional array of support openings 19 may be formed in thestaircase region 300. The substrate semiconductor layer 9 and thesemiconductor material layer 10 collectively constitutes a substrate (9,10), which may be a semiconductor substrate. Alternatively, thesemiconductor material layer 10 may be omitted, and the memory openings49 and the support openings 19 may be extend to a top surface of thesubstrate semiconductor layer 9.

FIGS. 5A-5G illustrate structural changes in a memory opening 49, whichis one of the memory openings 49 in the exemplary structure of FIGS. 4Aand 4B. The same structural change occurs simultaneously in each of theother memory openings 49 and in each of the support openings 19.

Referring to FIG. 5A, a memory opening 49 in the exemplary devicestructure of FIGS. 4A and 4B is illustrated. The memory opening 49extends through the insulating cap layer 70, the alternating stack (32,42), and optionally into an upper portion of the semiconductor materiallayer 10. At this processing step, each support opening 19 may extendthrough the retro-stepped dielectric material portion 65, a subset oflayers in the alternating stack (32, 42), and optionally through theupper portion of the semiconductor material layer 10. The recess depthof the bottom surface of each memory opening with respect to the topsurface of the semiconductor material layer 10 may be in a range from 0nm to 30 nm, although greater recess depths may also be used.Optionally, the sacrificial material layers 42 may be laterally recessedpartially to form lateral recesses (not shown), for example, by anisotropic etch.

Referring to FIG. 5B, an optional epitaxial pedestal channel 11 may beformed at the bottom portion of each memory opening 49 and each supportopening 19, for example, by performing a first selective epitaxyprocess. For example, the exemplary structure may be placed in a processchamber and heated to a deposition temperature, which may be in a rangefrom 600 degrees Celsius to 1,000 degrees Celsius. A semiconductorprecursor gas, an etchant gas, and a dopant gas including dopant atomsof the first conductivity type may be concurrently or alternately flowedinto the process chamber to induce deposition of a single crystallinesemiconductor material in epitaxial alignment with the singlecrystalline substrate semiconductor material of the semiconductormaterial layer 10 at the bottom of each memory opening 49 and at thebottom of each support opening 19. The deposited single crystallinesemiconductor material is herein referred to as a single crystallinepillar semiconductor material.

The semiconductor precursor gas comprises a gas that generatessemiconductor atoms upon dissociation. For example, the semiconductorprecursor gas may include one or more of silane (SiH₄), dichlorosilane(SiH₂Cl₂), trichlorosilane (SiHCl₃), silicon tetrachloride (SiCl₄),disilane (Si₂H₆), chlorinated derivatives of disilane, germane (GeH₄),digermane (Ge₂H₆), chlorinated derivatives of germane or digermane, andother precursor gases for a compound semiconductor material. The etchantgas may include a gas that may etch the semiconductor material formed bydecomposition of the semiconductor precursor gas. For example, theetchant gas may include gas phase hydrogen chloride (HCl).Alternatively, the etchant gas may be omitted if the semiconductorprecursor gas includes a chlorinated compound of a semiconductor elementand if hydrogen chloride may be generated by decomposition of thesemiconductor precursor gas. The dopant gas may be, for example, ahydride gas of dopants of the first conductivity type. If the firstconductivity type is p-type, the dopant gas may be diborane (B₂H₆). Ifthe first conductivity type is n-type, the dopant gas may includephosphine (PH₃), arsine (AsH₃), or stibine (SbH₃).

A carrier gas such as hydrogen, argon, or nitrogen may be used toprovide uniform gas flow in the process chamber. The flow rate of thecarrier gas may be adjusted such that the total pressure of the firstselective epitaxy process is in a range from 5 Torr to 200 Torr. If theprocess temperature is greater than 700 degrees Celsius, hydrogen orargon may be used as the carrier gas to prevent nitridation ofsemiconductor surfaces. A wet etch using hydrofluoric acid may beperformed prior to the first selective epitaxy process to remove surfaceoxide material from the physically exposed surfaces of the semiconductormaterial layer 10. A hydrogen anneal at an elevated temperature may beperformed to remove any native oxide and to provide atomically orderedsemiconductor surfaces before the first selective epitaxy process.

The first selective epitaxy process grows the epitaxial pedestalchannels 11 at bottom regions of the memory openings 49 and the supportopenings 19, while suppressing growth of any semiconductor material fromdielectric surfaces such as surfaces of the memory films 50, thealternating stack (32, 42), and the retro-stepped dielectric materialportion 65. The epitaxial pedestal channels 11 includes a singlecrystalline pillar semiconductor material that is in epitaxial alignmentwith the single crystalline substrate semiconductor material of thesemiconductor material layer 10 and the substrate semiconductor layer 9.

In one embodiment, the top surface of each epitaxial pedestal channel 11may be formed above a horizontal plane including the top surface of abottommost sacrificial material layer 42. In this case, a source selectgate electrode may be subsequently formed by replacing the bottommostsacrificial material layer 42 with a conductive material layer. Theepitaxial pedestal channel 11 may be a portion of a transistor channelthat extends between a source region to be subsequently formed in thesubstrate (9, 10) and a drain region to be subsequently formed in anupper portion of the memory opening 49. A memory cavity 49′ is presentin the unfilled portion of the memory opening 49 above the epitaxialpedestal channel 11.

In one embodiment, the epitaxial pedestal channels 11 may have a dopingof the first conductivity type, which is the same as the conductivitytype of the semiconductor material layer 10. If a semiconductor materiallayer 10 is not present, the epitaxial pedestal channel 11 may be formeddirectly on the substrate semiconductor layer 9, which may have a dopingof the first conductivity type. The atomic concentration of dopants ofthe first conductivity type in the epitaxial pedestal channels 11 may bein a range from 1.0×10¹⁴/cm³ to 1.0×10¹⁸/cm³, although lesser andgreater dopant concentrations may also be used.

Referring to FIG. 5C, a stack of layers including a blocking dielectriclayer 52, a charge storage layer 54, a tunneling dielectric layer 56,and an optional sacrificial cover material layer 601 may be sequentiallydeposited in the memory openings 49.

The blocking dielectric layer 52 may include a single dielectricmaterial layer or a stack of a plurality of dielectric material layers.In one embodiment, the blocking dielectric layer may include adielectric metal oxide layer consisting essentially of a dielectricmetal oxide. As used herein, a dielectric metal oxide refers to adielectric material that includes at least one metallic element and atleast oxygen. The dielectric metal oxide may consist essentially of theat least one metallic element and oxygen, or may consist essentially ofthe at least one metallic element, oxygen, and at least one non-metallicelement such as nitrogen. In one embodiment, the blocking dielectriclayer 52 may include a dielectric metal oxide having a dielectricconstant greater than 7.9, i.e., having a dielectric constant greaterthan the dielectric constant of silicon nitride.

Non-limiting examples of dielectric metal oxides include aluminum oxide(Al₂O₃), hafnium oxide (HfO₂), lanthanum oxide (LaO₂), yttrium oxide(Y₂O₃), tantalum oxide (Ta₂O₅), silicates thereof, nitrogen-dopedcompounds thereof, alloys thereof, and stacks thereof. The dielectricmetal oxide layer may be deposited, for example, by chemical vapordeposition (CVD), atomic layer deposition (ALD), pulsed laser deposition(PLD), liquid source misted chemical deposition, or a combinationthereof. The thickness of the dielectric metal oxide layer may be in arange from 1 nm to 20 nm, although lesser and greater thicknesses mayalso be used. The dielectric metal oxide layer may subsequently functionas a dielectric material portion that blocks leakage of storedelectrical charges to control gate electrodes. In one embodiment, theblocking dielectric layer 52 includes aluminum oxide. In one embodiment,the blocking dielectric layer 52 may include multiple dielectric metaloxide layers having different material compositions.

Alternatively, or additionally, the blocking dielectric layer 52 mayinclude a dielectric semiconductor compound such as silicon oxide,silicon oxynitride, silicon nitride, or a combination thereof. In oneembodiment, the blocking dielectric layer 52 may include silicon oxide.In this case, the dielectric semiconductor compound of the blockingdielectric layer 52 may be formed by a conformal deposition method suchas low pressure chemical vapor deposition, atomic layer deposition, or acombination thereof. The thickness of the dielectric semiconductorcompound may be in a range from 1 nm to 20 nm, although lesser andgreater thicknesses may also be used. Alternatively, the blockingdielectric layer 52 may be omitted, and a backside blocking dielectriclayer may be formed after formation of backside recesses on surfaces ofmemory films to be subsequently formed.

Subsequently, the charge storage layer 54 may be formed. In oneembodiment, the charge storage layer 54 may be a continuous layer orpatterned discrete portions of a charge trapping material including adielectric charge trapping material, which may be, for example, siliconnitride. Alternatively, the charge storage layer 54 may include acontinuous layer or patterned discrete portions of a conductive materialsuch as doped polysilicon or a metallic material that is patterned intomultiple electrically isolated portions (e.g., floating gates), forexample, by being formed within lateral recesses into sacrificialmaterial layers 42. In one embodiment, the charge storage layer 54includes a silicon nitride layer. In one embodiment, the sacrificialmaterial layers 42 and the insulating layers 32 may have verticallycoincident sidewalls, and the charge storage layer 54 may be formed as asingle continuous layer.

In another embodiment, the sacrificial material layers 42 may belaterally recessed with respect to the sidewalls of the insulatinglayers 32, and a combination of a deposition process and an anisotropicetch process may be used to form the charge storage layer 54 as aplurality of memory material portions that are vertically spaced apart.While the present disclosure is described using an embodiment in whichthe charge storage layer 54 is a single continuous layer, embodimentsare expressly contemplated herein in which the charge storage layer 54is replaced with a plurality of memory material portions (which may becharge trapping material portions or electrically isolated conductivematerial portions) that are vertically spaced apart.

The charge storage layer 54 may be formed as a single charge storagelayer of homogeneous composition, or may include a stack of multiplecharge storage layers. The multiple charge storage layers, if used, maycomprise a plurality of spaced-apart floating gate material layers thatcontain conductive materials (e.g., metal such as tungsten, molybdenum,tantalum, titanium, platinum, ruthenium, and alloys thereof, or a metalsilicide such as tungsten silicide, molybdenum silicide, tantalumsilicide, titanium silicide, nickel silicide, cobalt silicide, or acombination thereof) and/or semiconductor materials (e.g.,polycrystalline or amorphous semiconductor material including at leastone elemental semiconductor element or at least one compoundsemiconductor material). Alternatively or additionally, the chargestorage layer 54 may comprise an insulating charge trapping material,such as one or more silicon nitride segments. Alternatively, the chargestorage layer 54 may comprise conductive nanoparticles such as metalnanoparticles, which may be, for example, ruthenium nanoparticles. Thecharge storage layer 54 may be formed, for example, by chemical vapordeposition (CVD), atomic layer deposition (ALD), physical vapordeposition (PVD), or any suitable deposition technique for storingelectrical charges therein. The thickness of the charge storage layer 54may be in a range from 2 nm to 20 nm, although lesser and greaterthicknesses may also be used.

The tunneling dielectric layer 56 includes a dielectric material throughwhich charge tunneling may be performed under suitable electrical biasconditions. The charge tunneling may be performed through hot-carrierinjection or by Fowler-Nordheim tunneling induced charge transferdepending on the mode of operation of the monolithic three-dimensionalNAND string memory device to be formed. The tunneling dielectric layer56 may include silicon oxide, silicon nitride, silicon oxynitride,dielectric metal oxides (such as aluminum oxide and hafnium oxide),dielectric metal oxynitride, dielectric metal silicates, alloys thereof,and/or combinations thereof. In one embodiment, the tunneling dielectriclayer 56 may include a stack of a first silicon oxide layer, a siliconoxynitride layer, and a second silicon oxide layer, which is commonlyknown as an ONO stack. In one embodiment, the tunneling dielectric layer56 may include a silicon oxide layer that is substantially free ofcarbon or a silicon oxynitride layer that is substantially free ofcarbon. The thickness of the tunneling dielectric layer 56 may be in arange from 2 nm to 20 nm, although lesser and greater thicknesses mayalso be used.

The optional sacrificial cover material layer 601 includes a materialthat functions as an etch mask during subsequent anisotropic etch stepsthat etch through the tunneling dielectric layer 56, the charge storagelayer 54, and the blocking dielectric layer 52. Further, the material ofthe sacrificial cover material layer 601 may be selected such that thefirst cover material layer 601 may be subsequently removed selective tothe material of the tunneling dielectric layer 56 in an isotropic etchprocess. For example, the sacrificial cover material layer 601 mayinclude amorphous silicon, polysilicon, a silicon-germanium alloy,amorphous carbon, or a polymer material. The sacrificial cover materiallayer 601 may be formed by a conformal deposition method such as lowpressure chemical vapor deposition (LPCVD). The thickness of thesacrificial cover material layer 601 may be in a range from 2 nm to 10nm, although lesser and greater thicknesses may also be used. A memorycavity 49′ is formed in the volume of each memory opening 49 that is notfilled with the deposited material layers (52, 54, 56, 601).

Referring to FIG. 5D, the optional sacrificial cover material layer 601,the tunneling dielectric layer 56, the charge storage layer 54, and theblocking dielectric layer 52 may be sequentially anisotropically etchedusing at least one anisotropic etch process. The portions of thesacrificial cover material layer 601, the tunneling dielectric layer 56,the charge storage layer 54, and the blocking dielectric layer 52located above the top surface of the insulating cap layer 70 may beremoved by the at least one anisotropic etch process. Further, thehorizontal portions of the sacrificial cover material layer 601, thetunneling dielectric layer 56, the charge storage layer 54, and theblocking dielectric layer 52 at a bottom of each memory cavity 49′ maybe removed to form openings in remaining portions thereof. Each of thesacrificial cover material layer 601, the tunneling dielectric layer 56,the charge storage layer 54, and the blocking dielectric layer 52 may beetched by a respective anisotropic etch step using a respective etchchemistry, which may, or may not, be the same for the various materiallayers.

Each remaining portion of the sacrificial cover material layer 601 mayhave a tubular configuration. The charge storage layer 54 may comprise acharge trapping material or a floating gate material. In one embodiment,each charge storage layer 54 may include a vertical stack of chargestorage regions that store electrical charges upon programming. In oneembodiment, the charge storage layer 54 may be a charge storage layer inwhich each portion adjacent to the sacrificial material layers 42constitutes a charge storage region.

A surface of the epitaxial pedestal channel 11 may be physically exposedunderneath the opening through the sacrificial cover material layer 601,the tunneling dielectric layer 56, the charge storage layer 54, and theblocking dielectric layer 52 at the bottom of each memory cavity 49′ andat the bottom of each support cavity (which is an unfilled portion of asupport opening 19). A portion of the top surface of each epitaxialpedestal channel 11 may be vertically recessed from the bottom surfaceof the blocking dielectric layer 52 at the bottom of each memory opening49 by a recess distance.

A set of a blocking dielectric layer 52, a charge storage layer 54, anda tunneling dielectric layer 56 in a memory opening 49 constitutes amemory film 50, which includes a plurality of charge storage regions(comprising the charge storage layer 54) that are insulated fromsurrounding materials by the blocking dielectric layer 52 and thetunneling dielectric layer 56. Generally, a memory film 50 may beprovided by forming a charge storage layer 54 comprising a chargetrapping material within a memory opening 49, and by forming a tunnelingdielectric layer directly on the charge storage layer 54.

In one embodiment, the sacrificial cover material layer 601, thetunneling dielectric layer 56, the charge storage layer 54, and theblocking dielectric layer 52 may have vertically coincident sidewalls,i.e., sidewalls that are located within a same vertical plane. Eachmemory film 50 is formed on a top surface of a respective one of theepitaxial pedestal channels 11.

Referring to FIG. 5E, the sacrificial cover material layer 601 may beremoved selective to the material of the tunneling dielectric layer 56.For example, if the sacrificial cover material layer 601 includesamorphous carbon, the sacrificial cover material layer 601 may beremoved by ashing. If the sacrificial cover material layer 601 includesundoped amorphous silicon, a wet etch process using dilute trimethyl-2hydroxyethyl ammonium hydroxide (“TMY”), dilute tetramethyl ammoniumhydroxide (TMAH), or dilute KOH solution may be performed to remove thesacrificial cover material layer 601.

Referring to FIG. 5F, a second selective epitaxy process may beperformed to epitaxially grow a single crystalline semiconductormaterial, such as single crystal silicon, from each physically exposedsurface of the epitaxial pedestal channels 11. The single crystallinesemiconductor material is formed within each memory cavity 49′ such thatthe entire volume of each memory cavity 49′ is filled by the singlecrystalline semiconductor material. Excess portions of the singlecrystalline semiconductor material formed above a horizontal planeincluding the top surface of the insulating cap layer 70 may be removedby a planarization process such as a recess etch process and/or achemical mechanical planarization process. A single crystallinesemiconductor channel material portion 160 may be formed in each memoryopening 49. Each single crystalline semiconductor channel materialportion 160 may extend through an opening in a memory film 50, andcontact a bottom surface and a sidewall of an underlying epitaxialpedestal channel 11.

Each single crystalline semiconductor channel material portion 160 mayfill volumes of a memory opening 49 that is not filled with an epitaxialpedestal channel 11 and a memory film 50. The single crystallinesemiconductor channel material portions 160 may have a doping of a firstconductivity type, and may be in epitaxial alignment with the singlecrystalline substrate semiconductor material of the substrate (9, 10).The single crystalline semiconductor channel material portions 160 maybe formed directly on the tunneling dielectric layers 56.

The second selective epitaxy process may performed, for example, bydisposing the exemplary structure in a process chamber. The processchamber may be heated to a deposition temperature, which may be in arange from 850 degrees Celsius to 1,100 degrees Celsius, such as 900degrees Celsius to 1,050 degrees Celsius to provide a high depositionrate. A semiconductor precursor gas, an etchant gas, and a dopant gasincluding dopant atoms of the first conductivity type may beconcurrently or alternately flowed into the process chamber to inducedeposition of a single crystalline semiconductor material in epitaxialalignment with the single crystalline substrate semiconductor materialof the semiconductor material layer 10 at the bottom of each memoryopening 49 and at the bottom of each support opening 19.

The semiconductor precursor gas, the etchant gas, and the dopant gas maybe flowed into the process chamber while the exemplary structure is atthe deposition temperature. An externally supplied etchant gas isoptional if an etchant gas is generated as a byproduct of decompositionof the semiconductor precursor gas. The semiconductor precursor gascomprises a gas that generates semiconductor atoms upon dissociation. Inone embodiment, the semiconductor precursor gas may be selected toprovide a deposition rate greater than 100 nm per minute. The secondselective epitaxy process may use silane (SiH₄), dichlorosilane(SiH₂Cl₂), trichlorosilane (SiHCl₃), silicon tetrachloride (SiCl₄),disilane (Si₂H₆), chlorinated derivatives of disilane, germane (GeH₄),digermane (Ge₂H₆), chlorinated derivatives of germane or digermane, andother precursor gases for a compound semiconductor material. If asilicon containing precursor gas is used, then single crystallinesemiconductor channel material portions 160 comprise single crystalsilicon which may be grown at a growth rate in a range from 150 nm/minto 800 nm/min. If a germanium containing precursor gas is used, thensingle crystalline semiconductor channel material portions 160 comprisesingle crystal germanium. If a chlorine containing precursor gas is usedin a hydrogen carrier gas, then this may induce collateral formation ofhydrogen chloride gas that functions as an etchant. Alternatively, anetchant gas, such as hydrogen chloride may also be used. Thus, use of anadditional etchant gas such as an independently supplied hydrogenchloride gas is optional during the second selective epitaxy process.The dopant gas may be, for example, a hydride gas of dopants of thefirst conductivity type. If the first conductivity type is p-type, thedopant gas may be diborane (B₂H₆). If the first conductivity type isn-type, the dopant gas may include phosphine (PH₃), arsine (AsH₃), orstibine (SbH₃).

A carrier gas such as hydrogen, argon, or nitrogen may be used toprovide uniform gas flow in the process chamber. The flow rate of thecarrier gas may be adjusted such that the total pressure of the firstselective epitaxy process is in a range from 5 Torr to 200 Torr.Hydrogen or argon may be used as the carrier gas during the secondselective epitaxy process. A wet etch using hydrofluoric acid may beperformed prior to the second selective epitaxy process to removesurface oxide material from the physically exposed surfaces of theepitaxial pedestal channels 11. A hydrogen anneal at an elevatedtemperature may be performed to remove any native oxide and to provideatomically ordered semiconductor surfaces before the first selectiveepitaxy process.

The second selective epitaxy process may grow the single crystallinesemiconductor channel material portions 160 from physically exposedsemiconductor surfaces only, i.e., from the physically exposedsemiconductor surfaces of the epitaxial pedestal channels 11, whilesuppressing growth of any semiconductor material from dielectricsurfaces such as surfaces of the memory films 50, the alternating stack(32, 42), and the retro-stepped dielectric material portion 65. Thesingle crystalline semiconductor channel material portions 160 includesa single crystalline pillar semiconductor material that is in epitaxialalignment with the single crystalline substrate semiconductor materialof the semiconductor material layer 10 and the substrate semiconductorlayer 9 through the single crystalline semiconductor materials of theepitaxial pedestal channels 11.

The single crystalline semiconductor channel material portions 160 mayhave a doping of the first conductivity type, which is the same as theconductivity type of the semiconductor material layer 10 and theepitaxial pedestal channels 11. The atomic concentration of dopants ofthe first conductivity type in the single crystalline semiconductorchannel material portions 160 may be in a range from 1.0×10¹⁴/cm³ to1.0×10¹⁸/cm³, although lesser and greater dopant concentrations may alsobe used. The growth of the single crystalline semiconductor channelmaterial portions 160 is vertical, and thus, the single crystallinesemiconductor channel material portions 160 may be formed without voidstherein. In one embodiment, the entire volume of a single crystallinesemiconductor channel material portion 160 may be encapsulated bysurfaces of the single crystalline semiconductor channel materialportion 160, and may be filled only with the single crystallinesemiconductor material of the single crystalline semiconductor channelmaterial portion 160 without any cavity or any other material portiontherein. In one embodiment, each single crystalline semiconductorchannel material portion 160 may have a cylindrical shape and abottom-side protrusion that protrudes downward through an opening in amemory film 50. In one embodiment, the single crystalline semiconductorchannel material portions 160 may have a circular horizontalcross-sectional shape. In one embodiment, surfaces of each singlecrystalline semiconductor channel material portion 160 may include afirst cylindrical surface that contacts an inner cylindrical surface ofa memory film 50, an annular bottom surface that contacts an annularhorizontal surface of the memory film 50, a second cylindrical surfacethat contacts an opening through the memory film 50 and an innercylindrical sidewall of an underlying epitaxial pedestal channel 11, anda bottom surface that contacts a recessed surface of the underlyingepitaxial pedestal channel 11.

Referring to FIG. 5G, upper regions of the single crystallinesemiconductor channel material portions 160 may be converted into drainregions 63 by implantation of dopants of a second conductivity type,which is the opposite of the first conductivity type. For example, ifthe first conductivity type is p-type, the second conductivity type isn-type, and vice versa. Implantation of the dopants of the secondconductivity type may be performed by ion implantation or by plasmadoping. The drain regions 63 may have a net doping of the secondconductivity type with a net dopant concentration (i.e., the dopantconcentration for the second conductivity type dopants less the dopantconcentration for the first conductivity type dopants) in a range from5.0×10¹⁹/cm³ to 2.0×10²¹/cm³, although lesser and greater dopantconcentrations may also be used. Remaining regions of the singlecrystalline semiconductor channel material portions 160 constitutevertical semiconductor channels 60. Each combination of a memory film 50and a vertical semiconductor channel 60 constitutes a memory stackstructure 55.

Each memory stack structure 55 is a combination of a verticalsemiconductor channel 60, a tunneling dielectric layer 56, a chargestorage layer 54 that includes a vertical stack of memory elements(comprising portions of the charge storage layer 54 located at thelevels of the sacrificial material layers 42), and an optional blockingdielectric layer 52. Each combination of an epitaxial pedestal channel11 (if present), a memory stack structure 55, and a drain region 63within a memory opening 49 is herein referred to as a memory openingfill structure 58. Each combination of an epitaxial pedestal channel 11(if present), a memory film 50, a vertical semiconductor channel 60, anda drain region 63 within each support opening 19 fills the respectivesupport openings 19, and constitutes a support pillar structure.

Referring to FIG. 6, the exemplary structure is illustrated afterformation of memory opening fill structures 58 and support pillarstructure 20 within the memory openings 49 and the support openings 19,respectively. An instance of a memory opening fill structure 58 may beformed within each memory opening 49 of the structure of FIGS. 4A and4B. An instance of the support pillar structure 20 may be formed withineach support opening 19 of the structure of FIGS. 4A and 4B. While thepresent disclosure is described using an embodiment in which epitaxialpedestal channels 11 are used, embodiments are expressly contemplatedherein in which the vertical semiconductor channels 60 are formeddirectly on the semiconductor material layer 10 or the substratesemiconductor layer 9 without the epitaxial pedestal channels 11.

Each memory stack structure 55 extends through the alternating stack(32, 42), and comprises a respective memory film 50 and a respectivevertical semiconductor channel 60 including a single crystalline channelsemiconductor material. A crystallographic orientation of the singlecrystalline channel semiconductor material of the vertical semiconductorchannels 60 and a crystallographic orientation of the single crystallinesubstrate semiconductor material of the substrate (9, 10) that have asame Miller index are parallel to one other for each respective Millerindex. Thus, for any selected Miller index of the crystallographicstructure of the material of the vertical semiconductor channels 60, thespatial orientation for a crystallographic direction with the selectedMiller index in the vertical semiconductor channels 60 has the sameazimuthal angle θ and the same polar angle ϕ in a spherical coordinatesystem as the spatial orientation for the crystallographic directionwith the selected Miller index in the semiconductor material layer 10(if present) and in the substrate semiconductor layer 9.

Referring to FIGS. 7A and 7B, a contact level dielectric layer 73 may beformed over the alternating stack (32, 42) of insulating layer 32 andsacrificial material layers 42, and over the memory stack structures 55and the support pillar structures 20. The contact level dielectric layer73 includes a dielectric material that is different from the dielectricmaterial of the sacrificial material layers 42. For example, the contactlevel dielectric layer 73 may include silicon oxide. The contact leveldielectric layer 73 may have a thickness in a range from 50 nm to 500nm, although lesser and greater thicknesses may also be used.

A photoresist layer (not shown) may be applied over the contact leveldielectric layer 73, and is lithographically patterned to form openingsin areas between clusters of memory stack structures 55. The pattern inthe photoresist layer may be transferred through the contact leveldielectric layer 73, the alternating stack (32, 42) and/or theretro-stepped dielectric material portion 65 using an anisotropic etchto form backside trenches 79, which vertically extend from the topsurface of the contact level dielectric layer 73 at least to the topsurface of the substrate (9, 10), and laterally extend through thememory array region 100 and the staircase region 300.

In one embodiment, the backside trenches 79 may laterally extend along afirst horizontal direction hd1 and may be laterally spaced apart fromone another along a second horizontal direction hd2 that isperpendicular to the first horizontal direction hd1. The memory stackstructures 55 may be arranged in rows that extend along the firsthorizontal direction hd1. The drain select level isolation structures 72may laterally extend along the first horizontal direction hd1. Eachbackside trench 79 may have a uniform width that is invariant along thelengthwise direction (i.e., along the first horizontal direction hd1).Each drain select level isolation structure 72 may have a uniformvertical cross-sectional profile along vertical planes that areperpendicular to the first horizontal direction hd1 that is invariantwith translation along the first horizontal direction hd1. Multiple rowsof memory stack structures 55 may be located between a neighboring pairof a backside trench 79 and a drain select level isolation structure 72,or between a neighboring pair of drain select level isolation structures72. In one embodiment, the backside trenches 79 may include a sourcecontact opening in which a source contact via structure may besubsequently formed. The photoresist layer may be removed, for example,by ashing.

Referring to FIGS. 8 and 9A, an etchant that selectively etches thesecond material of the sacrificial material layers 42 with respect tothe first material of the insulating layers 32 may be introduced intothe backside trenches 79, for example, using an etch process. FIG. 9Aillustrates a region of the exemplary structure of FIG. 8. Backsiderecesses 43 may be formed in volumes from which the sacrificial materiallayers 42 are removed. The removal of the second material of thesacrificial material layers 42 may be selective to the first material ofthe insulating layers 32, the material of the retro-stepped dielectricmaterial portion 65, the semiconductor material of the semiconductormaterial layer 10, and the material of the outermost layer of the memoryfilms 50. In one embodiment, the sacrificial material layers 42 mayinclude silicon nitride, and the materials of the insulating layers 32and the retro-stepped dielectric material portion 65 may be selectedfrom silicon oxide and dielectric metal oxides.

The etch process that removes the second material selective to the firstmaterial and the outermost layer of the memory films 50 may be a wetetch process using a wet etch solution, or may be a gas phase (dry) etchprocess in which the etchant is introduced in a vapor phase into thebackside trenches 79. For example, in embodiments where the sacrificialmaterial layers 42 include silicon nitride, the etch process may be awet etch process in which the exemplary structure may be immersed withina wet etch tank including phosphoric acid, which etches silicon nitrideselective to silicon oxide, silicon, and various other materials used inthe art. The support pillar structure 20, the retro-stepped dielectricmaterial portion 65, and the memory stack structures 55 providestructural support while the backside recesses 43 are present withinvolumes previously occupied by the sacrificial material layers 42.

Each backside recess 43 may be a laterally extending cavity having alateral dimension that is greater than the vertical extent of thecavity. In other words, the lateral dimension of each backside recess 43may be greater than the height of the backside recess 43. A plurality ofbackside recesses 43 may be formed in the volumes from which the secondmaterial of the sacrificial material layers 42 is removed. The memoryopenings in which the memory stack structures 55 are formed are hereinreferred to as front side openings or front side cavities in contrastwith the backside recesses 43. In one embodiment, the memory arrayregion 100 comprises an array of monolithic three-dimensional NANDstrings having a plurality of device levels disposed above the substrate(9, 10). In such embodiments, each backside recess 43 may define a spacefor receiving a respective word line of the array of monolithicthree-dimensional NAND strings.

Each of the plurality of backside recesses 43 may extend substantiallyparallel to the top surface of the substrate (9, 10). A backside recess43 may be vertically bounded by a top surface of an underlyinginsulating layer 32 and a bottom surface of an overlying insulatinglayer 32. In one embodiment, each backside recess 43 may have a uniformheight throughout.

Physically exposed surface portions of the optional epitaxial pedestalchannels 11 and the semiconductor material layer 10 may be convertedinto dielectric material portions by thermal conversion and/or plasmaconversion of the semiconductor materials into dielectric materials. Forexample, thermal conversion and/or plasma conversion may be used toconvert a surface portion of each epitaxial pedestal channel 11 into atubular dielectric spacer 116, and to convert each physically exposedsurface portion of the semiconductor material layer 10 into a planardielectric portion 616. In one embodiment, each tubular dielectricspacer 116 may be topologically homeomorphic to a torus, i.e., generallyring-shaped. As used herein, an element is topologically homeomorphic toa torus if the shape of the element may be continuously stretchedwithout destroying a hole or forming a new hole into the shape of atorus. The tubular dielectric spacers 116 include a dielectric materialthat includes the same semiconductor element as the epitaxial pedestalchannels 11 and additionally includes at least one non-metallic elementsuch as oxygen and/or nitrogen such that the material of the tubulardielectric spacers 116 is a dielectric material. In one embodiment, thetubular dielectric spacers 116 may include a dielectric oxide, adielectric nitride, or a dielectric oxynitride of the semiconductormaterial of the epitaxial pedestal channels 11. Likewise, each planardielectric portion 616 may include a dielectric material that includesthe same semiconductor element as the semiconductor material layer andadditionally includes at least one non-metallic element such as oxygenand/or nitrogen such that the material of the planar dielectric portions616 is a dielectric material. In one embodiment, the planar dielectricportions 616 may include a dielectric oxide, a dielectric nitride, or adielectric oxynitride of the semiconductor material of the semiconductormaterial layer 10.

Referring to FIG. 9B, a backside blocking dielectric layer 44 may beoptionally formed. The backside blocking dielectric layer 44, ifpresent, comprises a dielectric material that functions as a controlgate dielectric for the control gates to be subsequently formed in thebackside recesses 43. In case the blocking dielectric layer 52 ispresent within each memory opening, the backside blocking dielectriclayer 44 is optional. In case the blocking dielectric layer 52 isomitted, the backside blocking dielectric layer 44 is present.

The backside blocking dielectric layer 44 may be formed in the backsiderecesses 43 and on a sidewall of the backside trench 79. The backsideblocking dielectric layer 44 may be formed directly on horizontalsurfaces of the insulating layers 32 and sidewalls of the memory stackstructures 55 within the backside recesses 43. If the backside blockingdielectric layer 44 is formed, formation of the tubular dielectricspacers 116 and the planar dielectric portion 616 prior to formation ofthe backside blocking dielectric layer 44 is optional. In oneembodiment, the backside blocking dielectric layer 44 may be formed by aconformal deposition process such as atomic layer deposition (ALD). Thebackside blocking dielectric layer 44 may consist essentially ofaluminum oxide. The thickness of the backside blocking dielectric layer44 may be in a range from 1 nm to 15 nm, such as 2 to 6 nm, althoughlesser and greater thicknesses may also be used.

The dielectric material of the backside blocking dielectric layer 44 maybe a dielectric metal oxide such as aluminum oxide, a dielectric oxideof at least one transition metal element, a dielectric oxide of at leastone Lanthanide element, a dielectric oxide of a combination of aluminum,at least one transition metal element, and/or at least one Lanthanideelement. Alternatively, or additionally, the backside blockingdielectric layer 44 may include a silicon oxide layer. The backsideblocking dielectric layer 44 may be deposited by a conformal depositionmethod such as chemical vapor deposition or atomic layer deposition. Thebackside blocking dielectric layer 44 is formed on the sidewalls of thebackside trenches 79, horizontal surfaces and sidewalls of theinsulating layers 32, the portions of the sidewall surfaces of thememory stack structures 55 that are physically exposed to the backsiderecesses 43, and a top surface of the planar dielectric portion 616. Abackside cavity 79′ is present within the portion of each backsidetrench 79 that is not filled with the backside blocking dielectric layer44.

Referring to FIG. 9C, a metallic barrier layer 46A may be deposited inthe backside recesses 43. The metallic barrier layer 46A includes anelectrically conductive metallic material that may function as adiffusion barrier layer and/or adhesion promotion layer for a metallicfill material to be subsequently deposited. The metallic barrier layer46A may include a conductive metallic nitride material such as TiN, TaN,WN, or a stack thereof, or may include a conductive metallic carbidematerial such as TiC, TaC, WC, or a stack thereof. In one embodiment,the metallic barrier layer 46A may be deposited by a conformaldeposition process such as chemical vapor deposition (CVD) or atomiclayer deposition (ALD). The thickness of the metallic barrier layer 46Amay be in a range from 2 nm to 8 nm, such as from 3 nm to 6 nm, althoughlesser and greater thicknesses may also be used. In one embodiment, themetallic barrier layer 46A may consist essentially of a conductive metalnitride such as TiN.

Referring to FIGS. 9D and 10, a metal fill material is deposited in theplurality of backside recesses 43, on the sidewalls of the at least onethe backside trench 79, and over the top surface of the contact leveldielectric layer 73 to form a metallic fill material layer 46B. Themetallic fill material may be deposited by a conformal depositionmethod, which may be, for example, chemical vapor deposition (CVD),atomic layer deposition (ALD), electroless plating, electroplating, or acombination thereof. In one embodiment, the metallic fill material layer46B may consist essentially of at least one elemental metal. The atleast one elemental metal of the metallic fill material layer 46B may beselected, for example, from tungsten, cobalt, ruthenium, titanium, andtantalum. In one embodiment, the metallic fill material layer 46B mayconsist essentially of a single elemental metal. In one embodiment, themetallic fill material layer 46B may be deposited using afluorine-containing precursor gas such as WF₆. In one embodiment, themetallic fill material layer 46B may be a tungsten layer including aresidual level of fluorine atoms as impurities. The metallic fillmaterial layer 46B is spaced from the insulating layers 32 and thememory stack structures 55 by the metallic barrier layer 46A, which is ametallic barrier layer that blocks diffusion of fluorine atomstherethrough.

A plurality of electrically conductive layers 46 may be formed in theplurality of backside recesses 43, and a continuous electricallyconductive material layer 46L may be formed on the sidewalls of eachbackside trench 79 and over the contact level dielectric layer 73. Eachelectrically conductive layer 46 includes a portion of the metallicbarrier layer 46A and a portion of the metallic fill material layer 46Bthat are located between a vertically neighboring pair of dielectricmaterial layers such as a pair of insulating layers 32. The continuouselectrically conductive material layer 46L includes a continuous portionof the metallic barrier layer 46A and a continuous portion of themetallic fill material layer 46B that are located in the backsidetrenches 79 or above the contact level dielectric layer 73.

Each sacrificial material layer 42 may be replaced with an electricallyconductive layer 46. A backside cavity 79′ may be present in the portionof each backside trench 79 that is not filled with the backside blockingdielectric layer 44 and the continuous electrically conductive materiallayer 46L. A tubular dielectric spacer 116 laterally surrounds anepitaxial pedestal channel 11. A bottommost electrically conductivelayer 46 laterally surrounds each tubular dielectric spacer 116 uponformation of the electrically conductive layers 46.

Referring to FIG. 11A, the deposited metallic material of the continuouselectrically conductive material layer 46L is etched back from thesidewalls of each backside trench 79 and from above the contact leveldielectric layer 73, for example, by an isotropic wet etch, ananisotropic dry etch, or a combination thereof. Each remaining portionof the deposited metallic material in the backside recesses 43constitutes an electrically conductive layer 46. Each electricallyconductive layer 46 may be a conductive line structure. Thus, thesacrificial material layers 42 are replaced with the electricallyconductive layers 46.

Each electrically conductive layer 46 may function as a combination of aplurality of control gate electrodes located at a same level and a wordline electrically interconnecting, i.e., electrically connecting, theplurality of control gate electrodes located at the same level. Theplurality of control gate electrodes within each electrically conductivelayer 46 are the control gate electrodes for the vertical memory devicesincluding the memory stack structures 55. In other words, eachelectrically conductive layer 46 may be a word line that functions as acommon control gate electrode for the plurality of vertical memorydevices.

In one embodiment, the removal of the continuous electrically conductivematerial layer 46L may be selective to the material of the backsideblocking dielectric layer 44. In this case, a horizontal portion of thebackside blocking dielectric layer 44 may be present at the bottom ofeach backside trench 79. In another embodiment, the removal of thecontinuous electrically conductive material layer 46L may not beselective to the material of the backside blocking dielectric layer 44or, the backside blocking dielectric layer 44 may not be used. Theplanar dielectric portions 616 may be removed during removal of thecontinuous electrically conductive material layer 46L. A backside cavity79′ is present within each backside trench 79.

Referring to FIGS. 12A and 12B, an insulating material layer may beformed in the backside trenches 79 and over the contact level dielectriclayer 73 by a conformal deposition process. Exemplary conformaldeposition processes include, but are not limited to, chemical vapordeposition and atomic layer deposition. The insulating material layerincludes an insulating material such as silicon oxide, silicon nitride,a dielectric metal oxide, an organosilicate glass, or a combinationthereof. In one embodiment, the insulating material layer may includesilicon oxide. The insulating material layer may be formed, for example,by low pressure chemical vapor deposition (LPCVD) or atomic layerdeposition (ALD). The thickness of the insulating material layer may bein a range from 1.5 nm to 60 nm, although lesser and greater thicknessesmay also be used.

If a backside blocking dielectric layer 44 is present, the insulatingmaterial layer may be formed directly on surfaces of the backsideblocking dielectric layer 44 and directly on the sidewalls of theelectrically conductive layers 46. If a backside blocking dielectriclayer 44 is not used, the insulating material layer may be formeddirectly on sidewalls of the insulating layers 32 and directly onsidewalls of the electrically conductive layers 46.

An anisotropic etch is performed to remove horizontal portions of theinsulating material layer from above the contact level dielectric layer73 and at the bottom of each backside trench 79. Each remaining portionof the insulating material layer constitutes an insulating spacer 74. Abackside cavity 79′ is present within a volume surrounded by eachinsulating spacer 74. A top surface of the semiconductor material layer10 may be physically exposed at the bottom of each backside trench 79.

A source region 61 may be formed at a surface portion of thesemiconductor material layer 10 under each backside cavity 79′ byimplantation of electrical dopants into physically exposed surfaceportions of the semiconductor material layer 10. Each source region 61is formed in a surface portion of the substrate (9, 10) that underlies arespective opening through the insulating spacer 74. Due to the straggleof the implanted dopant atoms during the implantation process andlateral diffusion of the implanted dopant atoms during a subsequentactivation anneal process, each source region 61 may have a lateralextent greater than the lateral extent of the opening through theinsulating spacer 74. Each source region 61 may be formed within thesingle crystalline substrate semiconductor material of the substrate (9,10), and has a doping of the second conductivity type.

Each upper portion of the semiconductor material layer 10 that extendsbetween the source region 61 and the plurality of epitaxial pedestalchannels 11 constitutes a horizontal semiconductor channel 59 for aplurality of field effect transistors. Each horizontal semiconductorchannel 59 is connected to multiple vertical semiconductor channels 60through respective epitaxial pedestal channels 11. Each horizontalsemiconductor channel 59 may contact a source region 61 and respectiveplurality of epitaxial pedestal channels 11. The horizontalsemiconductor channels 59 includes the single crystalline substratesemiconductor material of the substrate (9, 10), and have a doping ofthe first conductivity type.

A bottommost electrically conductive layer 46 provided upon formation ofthe electrically conductive layers 46 within the alternating stack (32,46) may comprise a select gate electrode for the field effecttransistors. Each source region 61 is formed in an upper portion of thesubstrate (9, 10). Semiconductor channels (59, 11, 60) extend betweeneach source region 61 and a respective set of drain regions 63. Thesemiconductor channels (59, 11, 60) include the vertical semiconductorchannels 60 of the memory stack structures 55.

A backside contact via structure 76 may be formed within each backsidecavity 79′. Each contact via structure 76 may fill a respective backsidecavity 79′. The contact via structures 76 may be formed by depositing atleast one conductive material in the remaining unfilled volume (i.e.,the backside cavity 79′) of the backside trench 79. For example, the atleast one conductive material may include a conductive liner 76A and aconductive fill material portion 76B. The conductive liner 76A mayinclude a conductive metallic liner such as TiN, TaN, WN, TiC, TaC, WC,an alloy thereof, or a stack thereof. The thickness of the conductiveliner 76A may be in a range from 3 nm to 30 nm, although lesser andgreater thicknesses may also be used. The conductive fill materialportion 76B may include a metal or a metallic alloy. For example, theconductive fill material portion 76B may include W, Cu, Al, Co, Ru, Ni,an alloy thereof, or a stack thereof.

The at least one conductive material may be planarized using the contactlevel dielectric layer 73 overlying the alternating stack (32, 46) as astopping layer. If chemical mechanical planarization (CMP) process isused, the contact level dielectric layer 73 may be used as a CMPstopping layer. Each remaining continuous portion of the at least oneconductive material in the backside trenches 79 constitutes a backsidecontact via structure 76.

The backside contact via structure 76 extends through the alternatingstack (32, 46), and contacts a top surface of the source region 61. If abackside blocking dielectric layer 44 is used, the backside contact viastructure 76 may contact a sidewall of the backside blocking dielectriclayer 44.

Referring to FIGS. 13A and 13B, additional contact via structures (88,86) may be formed through the contact level dielectric layer 73, andoptionally through the retro-stepped dielectric material portion 65. Forexample, drain contact via structures 88 may be formed through thecontact level dielectric layer 73 on each drain region 63. Word linecontact via structures 86 may be formed on the electrically conductivelayers 46 through the contact level dielectric layer 73, and through theretro-stepped dielectric material portion 65.

Referring to FIG. 14, memory-side dielectric material layers 960 may bedeposited over the contact level dielectric layer 73. Variousmemory-side metal interconnect structures 980 may be formed in thememory-side dielectric material layers 960. The memory-side metalinterconnect structures 980 may include bit lines 98 that overlie thememory stack structures 55 and electrically connected to a respectivesubset of the drain regions 63. Further, the memory-side metalinterconnect structures 980 may include additional metal via structuresand additional metal line structures that provide electrical wiring toand from the various underlying elements such as the backside contactvia structures 76, the word line contact via structures 86, the bitlines 98, and other nodes of the three-dimensional memory device thatmay be formed as needed. The thickness of the memory-side dielectricmaterial layers 960 may be in a range from 300 nm to 3,000 nm, althoughlesser and greater thicknesses may also be used.

Pad cavities may be formed in the upper portion of the memory-side metalinterconnect structures 980 such that a respective one of thememory-side metal interconnect structures 980 is exposed at the bottomof each pad cavity. In one embodiment, the pad cavities may be arrangedas a one-dimensional array or as a two-dimensional array, and may have arespective polygonal, circular, elliptical, or generally-curvilinearshape. A conductive material may be deposited in the pad cavities toform various memory-side bonding pads 988. The memory-side bonding pads988 may be formed within memory-side dielectric material layers 960,which is formed over the alternating stack (32, 46). The memory-sidebonding pads 988 may be electrically connected to nodes of the memorystack structures 55. In one embodiment, each bit line 98 may beelectrically connected to a respective one of the memory-side bondingpads 988. The exemplary structure comprises a memory die 900.

Referring to FIG. 15, a support die 700 is provided, which comprisesvarious semiconductor devices 710 formed on a support-die substrate 708.The support-die substrate 708 may include at least one elementalsemiconductor material (e.g., single crystal silicon wafer or layer), atleast one III-V compound semiconductor material, at least one II-VIcompound semiconductor material, at least one organic semiconductormaterial, or other semiconductor materials known in the art.

The semiconductor devices 710 includes a peripheral circuitry configuredto control operation of memory elements in the memory stack structures55 in the memory die 900. The peripheral circuitry may include a wordline driver that drives word lines of the three-dimensional memory array(comprising the electrically conductive layers 46) within the memory die900, a bit line driver that drives the bit lines 98 in the memory die900, a word line decoder circuit that decodes the addresses for theelectrically conductive layers 46, a bit line decoder circuit thatdecodes the addresses for the bit lines 98, a sense amplifier circuitthat senses the states of memory elements within the memory stackstructures 55 in the memory die 900, a source power supply circuit thatprovides power to source regions 61 the memory die 900, a data bufferand/or latch, or any other semiconductor circuit that may be used tooperate the array of memory stack structures 55 in the memory die 900.

The various semiconductor devices 710 may include field effecttransistors, which include respective transistor active regions (i.e.,source regions and drain regions), a channel, and a gate structure. Thefield effect transistors may be arranged in a CMOS configuration.Dielectric material layers are formed over the semiconductor devices710, which are herein referred to as support-side dielectric materiallayers 760. Support-side metal interconnect structures 780 may be formedwithin the support-side dielectric material layers 760. The support-sidemetal interconnect structures 780 may include various device contact viastructures (e.g., source and drain electrodes which contact therespective source and drain nodes of the device or gate electrodecontacts), interconnect-level metal line structures, interconnect-levelmetal via structures, and support-side bonding pads 788. Thesupport-side bonding pads 788 may be formed in support-side dielectricmaterial layers 760, and are electrically connected to nodes of theperipheral circuitry. The support-side bonding pads 788 are configuredto mate with the memory-side bonding pads 988 of a memory die 900 toprovide electrically conductive paths between the memory die 900 and thesupport die 700.

Referring to FIG. 16, an exemplary bonded assembly according to anembodiment of the present disclosure is illustrated, which may be formedby bonding the memory-side bonding pads 988 of the memory die 900 to thesupport-side bonding pads 788 of the support die 700. Metal-to-metalbonding may be used to bond the memory die 900 to the support die 700.

The support-die substrate 708 may be thinned, for example, by grinding,chemical etching, polishing, or a combination thereof. The thickness ofthe support-die substrate 708 as thinned may be in a range from 0.5micron to 5 microns, although lesser and greater thicknesses may also beused. A backside insulating layer 714 may be formed on the backsidesurface of the support-die substrate 708. The backside insulating layer714 includes an insulating material such as silicon oxide, and may havea thickness in a range from 30 nm to 600 nm, although lesser and greaterthicknesses may also be used. Through-substrate via cavities may beformed through the support-die substrate 708. An insulating spacer 711and a through-substrate conductive via structure 712 may be formed ineach of the substrate via cavities. An external bonding pad 716 may beformed on each through-substrate contact via structure 712. A solderball (not shown) may be applied to each external bonding pad 716, and abonding wire (not shown) may be attached to each solder ball.

Referring to all drawings and according to various embodiments of thepresent disclosure, a semiconductor structure comprising a memory die900 bonded to a support die 700 containing peripheral circuitry isprovided. The memory die 900 comprises: an alternating stack ofinsulating layers 32 and electrically conductive layers 46 located overa substrate (9, 10) including a single crystalline substratesemiconductor material; memory stack structures 55 extending through thealternating stack (32, 46) and comprising a respective memory film 50and a respective vertical semiconductor channel 60 including a singlecrystalline channel semiconductor material.

In one embodiment, the memory die 900 comprises memory-side bonding pads988 formed within memory-side dielectric material layers 960 thatoverlie the alternating stack (32, 46) and electrically connected tonodes of the memory stack structures 55. In one embodiment, the supportdie 700 comprises support-side bonding pads 788 formed withinsupport-side dielectric material layers 760, electrically connected tonodes of the peripheral circuitry, and bonded to the memory-side bondingpads 988.

In one embodiment, a crystallographic orientation of the singlecrystalline channel semiconductor material and a crystallographicorientation of the single crystalline substrate semiconductor materialthat have a same Miller index are parallel to one other for eachrespective Miller index. The memory die 900 comprises epitaxial pedestalchannels 11 comprising a respective single crystalline pillarsemiconductor material in epitaxial alignment with the singlecrystalline substrate semiconductor material and with the singlecrystalline channel semiconductor material of an overlying one of thevertical semiconductor channels 60.

In one embodiment, the memory die 900 comprises drain regions 63comprising a single crystalline drain semiconductor material inepitaxial alignment with the single crystalline channel semiconductormaterial of an underlying one of the vertical semiconductor channels 60.In one embodiment, the single crystalline channel semiconductor materialand the single crystalline pillar semiconductor material includesdopants of a first conductivity type at a first atomic concentration,and the single crystalline drain semiconductor material includes dopantsof a second conductivity type that is an opposite of the firstconductivity type at a second atomic concentration that is greater thanthe first atomic concentration.

In one embodiment, the memory die 900 comprises a source region 61formed within the single crystalline substrate semiconductor material ofthe substrate (9, 10) and having a doping of the second conductivitytype, and a backside contact via structure 76 extending through thealternating stack (32, 46) and contacting the source region 61. Thesingle crystalline substrate semiconductor material of the substrate (9,10) has a doping of the first conductivity type. In one embodiment, thememory die 900 comprises bit lines 98 that overlie the memory stackstructures 55 and electrically connected to a respective subset of thedrain regions 63 and electrically connected to a respective one of thememory-side bonding pads 988.

In one embodiment, each of the memory films 50 laterally surrounds, andcontacts, a respective one of the vertical semiconductor channels 60,and overlies, and contacts, a respective one of the epitaxial pedestalchannels 11.

In one embodiment, each of the memory films 50 comprises: a cylindricalportion that contacts sidewalls of the insulating layers 32 within thealternating stack (32, 46), and an annular portion that adjoins a bottomend of the cylindrical portion. One of the vertical semiconductorchannels 60 extends through an opening through the annular portion. Inone embodiment, a top surface of the annular portion contacts an annularbottom surface of the one of the vertical semiconductor channels 60, abottom surface of the annular portion contacts a top surface of anunderlying one of the epitaxial pedestal channels 11. In one embodiment,an entire bottom surface of each of the drain regions 63 contacts anentire top surface of an underlying one of the vertical semiconductorchannels 60.

In one embodiment, each of the memory films 50 comprises a chargestorage layer 54 comprising a charge trapping material and verticallyextending through the alternating stack (32, 46) as a continuousmaterial layer, and a tunneling dielectric layer 56 contacting an innersidewall of the charge storage layer 54 and laterally surrounding, andcontacting, a respective one of the vertical semiconductor channels 60.

In one embodiment, the alternating stack (32, 46) comprises a terraceregion in which each electrically conductive layer 46 other than atopmost electrically conductive layer 46 within the alternating stack(32, 46) laterally extends farther than any overlying electricallyconductive layer 46 within the alternating stack (32, 46) to providestepped surfaces, a retro-stepped dielectric material portion 65overlying the stepped surfaces, and contact via structures (such as wordline contact via structure 86) extending through the retro-steppeddielectric material portion 65 and contacting a respective one of theelectrically conductive layers 46.

The exemplary structures may include a three-dimensional memory device.In one embodiment, the three-dimensional memory device comprises amonolithic three-dimensional NAND memory device. The electricallyconductive layers 46 may comprise, or may be electrically connected to,a respective word line of the monolithic three-dimensional NAND memorydevice. The substrate (9, 10) may comprise a silicon substrate. Thevertical NAND memory device may comprise an array of monolithicthree-dimensional NAND strings over the silicon substrate. At least onememory cell (comprising a portion of a charge storage layer 54 at alevel of an electrically conductive layer 46) in a first device level ofthe array of monolithic three-dimensional NAND strings may be locatedover another memory cell (comprising another portion of the chargestorage layer 54 at a level of another electrically conductive layer 46)in a second device level of the array of monolithic three-dimensionalNAND strings. The electrically conductive layers 46 may comprise aplurality of control gate electrodes having a strip shape extendingsubstantially parallel to the top surface of the substrate (9, 10),e.g., between a pair of backside trenches 79. The plurality of controlgate electrodes comprises at least a first control gate electrodelocated in a first device level and a second control gate electrodelocated in a second device level. The array of monolithicthree-dimensional NAND strings may comprise: a plurality ofsemiconductor channels (59, 11, 60), wherein at least one end portion(such as a vertical semiconductor channel 60) of each of the pluralityof semiconductor channels (59, 11, 60) extends substantiallyperpendicular to a top surface of the substrate (9, 10) and comprising arespective one of the vertical semiconductor channels 60; and aplurality of charge storage elements (comprising portions of the memoryfilms 50, i.e., portions of the charge storage layer 54). Each chargestorage element may be located adjacent to a respective one of theplurality of semiconductor channels (59, 11, 60).

The vertical semiconductor channels 60 of the memory die 900 include thesingle crystalline semiconductor channel material, which providesenhanced charge carrier mobility compared to polycrystallinesemiconductor channel materials known in the art. The enhanced chargecarrier mobility increases the on-current of the vertical semiconductorchannels 60, and provides stacking of a greater number of electricallyconductive layers 46 as word lines, thereby increasing the devicedensity in a three-dimensional memory device. The single crystallinechannel semiconductor material may also be formed by a high rate CVDepitaxial growth process at a relatively high temperature withoutdamaging the peripheral circuitry transistors because the peripheralcircuitry is formed on a separate support die and bonded to the memorydie after formation of the vertical semiconductor channels.

Although the foregoing refers to particular preferred embodiments, itwill be understood that the disclosure is not so limited. It will occurto those of ordinary skill in the art that various modifications may bemade to the disclosed embodiments and that such modifications areintended to be within the scope of the disclosure. Compatibility ispresumed among all embodiments that are not alternatives of one another.The word “comprise” or “include” contemplates all embodiments in whichthe word “consist essentially of” or the word “consists of” replaces theword “comprise” or “include,” unless explicitly stated otherwise. Wherean embodiment using a particular structure and/or configuration isillustrated in the present disclosure, it is understood that the presentdisclosure may be practiced with any other compatible structures and/orconfigurations that are functionally equivalent provided that suchsubstitutions are not explicitly forbidden or otherwise known to beimpossible to one of ordinary skill in the art. All of the publications,patent applications and patents cited herein are incorporated herein byreference in their entirety.

What is claimed is:
 1. A semiconductor structure comprising a memory diebonded to a support die, wherein: the memory die comprises analternating stack of insulating layers and electrically conductivelayers located over a substrate including a single crystalline substratesemiconductor material, and memory stack structures extending throughthe alternating stack and comprising a respective memory film and arespective vertical semiconductor channel including a single crystallinechannel semiconductor material; and the support die comprises aperipheral circuitry.
 2. The semiconductor structure of claim 1,wherein: the memory die further comprises memory-side bonding padsformed within memory-side dielectric material layers that overlie thealternating stack and electrically connected to nodes of the memorystack structures; and the support die further comprises support-sidebonding pads formed within support-side dielectric material layers,electrically connected to nodes of the peripheral circuitry and bondedto the memory-side bonding pads.
 3. The semiconductor structure of claim1, wherein: the single crystalline channel semiconductor materialcomprises single crystal silicon; a crystallographic orientation of thesingle crystalline channel semiconductor material and a crystallographicorientation of the single crystalline substrate semiconductor materialhaving a same Miller index are parallel to one other for each respectiveMiller index; and the memory die comprises epitaxial pedestal channelscomprising a respective single crystalline pillar semiconductor materialin epitaxial alignment with the single crystalline substratesemiconductor material and with the single crystalline channelsemiconductor material of an overlying one of the vertical semiconductorchannels.
 4. The semiconductor structure of claim 3, wherein the memorydie further comprises drain regions comprising a single crystallinedrain semiconductor material in epitaxial alignment with the singlecrystalline channel semiconductor material of an underlying one of thevertical semiconductor channels.
 5. The semiconductor structure of claim4, wherein the memory die further comprises bit lines that overlie thememory stack structures and electrically connected to a respectivesubset of the drain regions and electrically connected to a respectiveone of the memory-side bonding pads.
 6. The semiconductor structure ofclaim 3, wherein each of the memory films laterally surrounds, andcontacts, a respective one of the vertical semiconductor channels, andoverlies, and contacts, a respective one of the epitaxial pedestalchannels.
 7. The semiconductor structure of claim 6, wherein each of thememory films comprises: a cylindrical portion that contacts sidewalls ofthe insulating layers within the alternating stack; and an annularportion that adjoins a bottom end of the cylindrical portion, whereinone of the vertical semiconductor channels extends through an openingthrough the annular portion.
 8. The semiconductor structure of claim 7,wherein: a top surface of the annular portion contacts an annular bottomsurface of the one of the vertical semiconductor channels; and a bottomsurface of the annular portion contacts a top surface of an underlyingone of the epitaxial pedestal channels.
 9. The semiconductor structureof claim 7, wherein an entire bottom surface of each of the drainregions contacts an entire top surface of an underlying one of thevertical semiconductor channels.
 10. The semiconductor structure ofclaim 1, wherein each of the memory films comprises: a charge storagelayer comprising a charge trapping material and vertically extendingthrough the alternating stack as a continuous material layer; and atunneling dielectric layer contacting an inner sidewall of the chargestorage layer and laterally surrounding, and contacting, a respectiveone of the vertical semiconductor channels.
 11. The semiconductorstructure of claim 1, further comprising: a terrace region in which eachelectrically conductive layer other than a topmost electricallyconductive layer within the alternating stack laterally extends fartherthan any overlying electrically conductive layer within the alternatingstack to provide stepped surfaces; a retro-stepped dielectric materialportion overlying the stepped surfaces; and contact via structuresextending through the retro-stepped dielectric material portion andcontacting a respective one of the electrically conductive layers.